1. Field of the Invention
The present invention relates to a connection terminal for connecting at least two lines, comprising a first clamping block to which a first line can be electrically and mechanically connected and a second clamping block to which a second line can be electrically and mechanically connected.
2. Related Prior Art
Such connection terminals are generally known in the prior art.
These connection terminals are available for example in specialty stores as individual parts and are used for example to connect lamps to electrical lines. For this purpose, such connection terminals normally comprise at least two connection parts each consisting of two clamping blocks of electrically conducting material, which are integrally connected to one another, as well as an insulating casing in which the connection parts are arranged.
Each connection part comprises a retaining through bore as well as threaded bores running transversely thereto. The ends, with their insulation removed, of the lines to be connected are inserted into the retaining bores on either side, and these ends are clamped in the retaining bores by screws screwed into the threaded bores. In this manner, a pair of two lines can be electrically and mechanically coupled by a single connecting part. It is also known to insert several lines at one side in the retaining bore, so that an incoming line can simultaneously be connected with several outgoing lines.
Such connection terminals are generally known as lustre terminals.
On the other hand, such connection terminals are also used for connecting transformers, motors, etc. It is known to configure such connection terminals directly, integrally with the housing of the device to be connected, although the connection terminals can also be formed as separate parts secured to the housing of the electrical device by screws or locking.
It is also known to configure the clamping block not as screw connectors but as insulation displacement connectors, where cutting elements are provided in the retaining bores between which the inserted line is clamped and simultaneously contacted.
A so-called temperature limiter is necessary for safety reasons in numerous electrical devices, which normally comprises a bimetal switch and is connected in series with a supply line of the electrical device, so that the operating current of the electrical device flows through the temperature limiter. The temperature limiter is normally thermally coupled to the electrical device to be protected by the limiter, so that a temperature increase of the electrical device leads to a temperature increase of the temperature limiter.
When the temperature of the electrical device to be protected exceeds an allowable upper limit, a bimetal element disposed in the switch is deformed in a known manner and interrupts the current flow to the electrical device. Depending on the configuration of the temperature limiter, it can be provided with a so-called self-holding function, which ensures that the temperature limiter does not switch on again even after the electrical device has cooled off.
It is also known to provide such temperature limiters with a current dependency, so that they respond additionally or exclusively when a certain current value is exceeded, whereby the electrical device is protected against an excess current.
The mounting of such temperature limiters on an electrical device to be protected, normally by hand, is done independently of the connection of the electrical device itself by means of the above-mentioned connection terminal. Frequently, connecting lines of the temperature limiter must be soldered onto contacts of the electrical device to be protected.
An electrical device is known from DE 195 05 342, in which a receptacle is provided for an encapsulated temperature dependent switching mechanism, which is clamped between an external terminal of the device and a terminal part connected directly to the device. From this document, it is also known to provide a receptacle space at the electrical device into which two connecting elements extend between which the encapsulated temperature dependent switch is clamped. A short circuit plug can also be inserted instead of the temperature dependent switch to test the electrical device during fabrication before mounting the temperature dependent switch.
All of the discussed measures for connecting a temperature dependent switch or temperature limiter to an electrical device to be protected have the disadvantage that they either cannot be automated at all or require complicated manipulations, where, for example, first a short circuit plug is plugged in, removed after testing and then the desired temperature dependent switch is inserted.
In view of the above, an object of the present invention is to provide a simplified, preferably automated assembly of an electrical device equipped with a temperature limiter, where the solution should have a simple construction.
According to the present invention, this object is essentially solved in that the connection terminal as mentioned at the outset comprises a receptacle into which a temperature limiter comprising at least two terminals, preferably two terminal legs, can be plugged in, and into which two connection elements extend, each being connected at their first end to one of the two clamping blocks and at their second end, preferably automatically, contacting a terminal, preferably an associated terminal leg of a temperature limiter, when plugging in same in the receptacle.
The inventors of the present application have found that surprisingly structural modifications of the connection terminal allow a plug-in contact of the temperature limiter so that a series connection of the temperature limiter between the clamping blocks results by simply plugging in the temperature limiter in the receptacle, so that the temperature limiter can be arranged in series with the supply line of the electrical device. This procedure can be automated, because after wiring the connection element the only additional step is to plug in the temperature limiter. Contacting of the temperature limiter to the connection elements is established for example by the insulation displacement technique, although it is also possible to provide screw clamping means. In this case, after plugging in the temperature limiter in the receptacle, only two screws need be tightened down, which however can also be performed automatically, as is the case with wiring the connection element to the lines.
Furthermore, the new connection element allows a rapid and simple assembly and connection of the temperature limiter by hand, for example when a small lot is to be produced or the devices are produced with a lesser degree of automisation.
The new connection terminal can not only be employed for the protection of transformers, motors, etc., where it is secured to the housing in one way or another, rather it can also be used in various fields where protection by a temperature limiter of a device to be connected is possible retroactively in the simplest manner. For example, it is possible to replace the common lustre terminal on a lighting means with the new connection terminal, which only requires a few hand manipulations. With the new connection terminal including the inserted temperature limiter it is now, for example, possible to protect against overheating lighting means previously unmonitored with respect to their temperature development. As is generally known, the lustre clamps in the housing of the lighting means are frequently arranged directly adjacent to the lamp means, so that an overheating results when the rating of the lamp means is too high, which then leads to an increase in the temperature of the lustre clamp, which can be seen over and again with lustre clamps that are charred or deformed by the effects of heat. If the new connection terminals are used instead of the known lustre clamps, an inadmissibly high temperature has the result that the power supply to the lighting means is shut off by the temperature limiter, so that it cannot be damaged or cause any damage as a result of overheating.
In view of the above, connection terminals of the above-mentioned type are subject of the present invention, which comprise between the two clamping blocks a temperature limiter with any interconnection, also for example by soldering the temperature limiter being connected in series with the clamping blocks. By simply exchanging a lustre clamp or by inserting it into a supply line for this purpose, it is possible with the new connection terminal to equip different electrical devices, even retroactively, with a temperature and/or current monitoring means.
Suitable temperature dependent switches are known from documents DE 196 09 310 A1, DE 197 47 589 A1 and DE 197 52 581, each including arranged within a housing a temperature dependent switching mechanism that can be contacted by means of terminal legs extending from the housing, and that according to the first document mainly shows a dependency from temperature, according to the second document a self-holding function, and according to the third document a current dependency.
It should be mentioned that, in the scope of the present application, xe2x80x9ctemperature limiterxe2x80x9d is, on the one hand, generally to be understood as a temperature dependent switch, which separates an electrical connection when an high temperature and/or excess current arises and which optionally is provided with a self-holding function which prevents a closing of the switch after cooling off, wherein in certain configurations the switch remains open even after shutting off the power source, while in other configurations, the self-holding function is reset when the power supply is turned off and then on again. On the other hand xe2x80x9ctemperature limitersxe2x80x9d is here also to be understood as PTC resistors whose resistance increases with growing temperature, so that a current limitation and, indirectly, a temperature limitation is provided for.
As a matter of course it is also possible to integrate the present connection terminal in power switches or plug sockets, couplings, etc. to prevent an inadmissible heating and/or inadmissible high current through the connected consumers. Advantages result, in particular for use outdoors, for example with a water pump in a pond, a garden lamp or the like, which can be inexpensively and simply protected, also when retrofitted.
In an embodiment, the two connection elements at their second end each comprise a clamp contact for an associated terminal leg of the temperature limiter.
This feature is of advantage with respect to simple assembly, since the temperature limiter must only be plugged in and drawing down of additional screws is not necessary.
According to a further object an interruptable short circuit connection is provided between the two connection elements at their second ends, which preferably is interrupted by an actuator member insertable into the receptacle, this actuator member being either arranged on the temperature limiter or provided as a breaker pin, which is insertable into the receptacle so as not to be removable.
These features are generally of advantage in that the connection terminal can be used without the inserted temperature limiter, where no special short circuit plug need be plugged into the receptacle, but the short circuit connection is provided automatically, so to speak, by the temperature limiter not yet having been inserted.
In this manner, one can decide which temperature limiter is to be assembled just before using the new connection terminal. It is, for example, possible to test the electrical device initially without the temperature limiter and then to plug in the limiter, which also can take place automatically, depending on the specifications just before delivering the device. These measures are also of advantage when the present terminals are used to replace lustre clamps, since the entire wiring and cable connections can first be made and tested before upon choice different temperature limiters can then be inserted. This means that the present connection terminal can be marketed independently of the temperature limiter, where it is naturally also possible to market connection terminals with installed temperature limiters, optionally soldered-in temperature limiters.
A further advantage is that the interruption of the short circuit connection does not require the removal of a short circuit plug or the like, rather it is achieved by an actuator member which can also easily and automatically be inserted. A particular advantage is achieved when the actuator member is arranged on the temperature limiter, as then only a single hand manipulation is necessary to simultaneously interrupt the short circuit connection and install the temperature limiter.
The breaker pin has the further advantage that it fulfills special safety requirements when configured to be non-removable. A connection terminal once having been equipped with a temperature limiter can then no more be operated without the temperature limiter, so that a device supplied with power via the connection terminal and to be protected by the inserted temperature limiter can only be supplied with power when the temperature limiter is in place. Should the temperature limiter fall out or be deliberately removed, the device is no longer be supplied with power, so that a high degree of safety with respect to monitoring of the temperature and current is guaranteed. The breaker pin can, for example, be locked in the receptacle for this purpose.
According to a further object, the breaker pin is insertable into the receptacle in a force fit, which can be achieved for example when it has a zero tolerance or a slightly larger dimension with respect to the receptacle.
In this very simple constructive manner, it is ensured that the breaker pin cannot be removed or removed only by destroying the connection terminal.
It will be understood however that the temperature limiter can be exchanged, should it be defective or be exchanged with another temperature limiter with other specifications, for example another response temperature.
It is a further object that the short circuit connection comprises a short circuit element clamped between the connection elements and being movable to an open position by the actuator member.
Also this feature is constructively preferred as it is only necessary to provide a resilient part on one connection element, which is biased onto the other connection element and lifted thereoff by the actuator member. The resilient part can be broken or broken off by the actuator member, so that reestablishing the short circuit connection is excluded. Alternatively, it is also possible to provide the short circuit means as a connector block, which is pushed out of the gap between the two connection elements by the actuator member and optionally urged into a clamp seat from which it cannot be removed, so that an inadvertent closing of the short circuit connection is not possible.
It is a further object that the two connection elements each comprise at least one resilient element and the two resilient elements contact one another to establish the short circuit connection and can be separated from one another by the actuator member.
This has the advantage that two resilient elements contribute to the quality of the short circuit connection, so that a very reliable short circuit connection exists between the clamping blocks before inserting the temperature limiter.
According to a further object each resilient element comprises a first contact region through which it forms the short circuit connection with the first contact region of the other resilient element, and a second contact region through which it contacts an associated terminal leg of a temperature limiter when inserted in the receptacle.
Also this measure is constructively advantageous because each connector element requires only one resilient element which establishes either the short circuit connection or the contact to the temperature limiter. A further advantage apart from the simple construction is that an inserted temperature limiter cannot be bypassed again by inadvertently closing the short circuit connection because the resilient elements can only contact one another or the terminal legs of the temperature limiter.
According to a further object the two connection elements at their respective first end are spring biased into contact with the respective clamping block, where preferably at least one of the clamping blocks comprises a retaining bore for receiving a line as well as a threaded hole running transversely to the bore for a screw for clamping the line in the retaining bore, where preferably the two connection elements on their respective first ends comprise an up-standing resilient wing, which extends approximately parallel to the respective screw and is spring biased onto the screw.
These measures are advantageous in that convential clamping blocks can be used, as are known from the common lustre clamps. Contact results through the connection elements which are either resiliently urged onto the clamping block itself or are urged with their wing onto the clamping screw for the line. An advantage of the wing is also that it can compensate for different geometries of the screw, where the contact further is not impaired when lines of different thickness are clamped in the retaining bore, i.e. when the screw is screwed into the threaded hole at different depths to clamp the line or lines.
It is another object that the connection terminal comprises at least one connection part having two clamping blocks directly connected to one another, through which two further lines can be directly connected to one another.
The advantage is that the present connection terminal can connect two lines directly with one another, while two further lines are connected to one another in series connection with the temperature limiter. The inventors of the present application have found that it is not necessary to provide a temperature limiter in every supply line of the electrical device, although this can naturally be of advantage in certain requirement circumstances, for example when a current dependent temperature limiter without the self-holding function and additionally a temperature limiter responding solely to high temperatures with self-holding function are to be used simultaneously.
According to a further object the connection terminal comprises an insulating casing in which the first and second clamping blocks are arranged at a first side and the connecting part is arranged at a second side and the receptacle is arranged between the two sides.
This allows a geometry such that the temperature limiter is located so to speak in the middle of the connection terminal, where naturally a location at the side is also possible.
According to another object the connection terminal comprises an insulating casing having a first casing section receiving the first and second clamping block and at least one second casing section receiving the at least one connection part, where a flexible spacer is provided between the two casing sections such that the two casing sections are variable in their spacing laterally to one another.
This measure has the advantage that the new connection terminal can also be used to connect at least two pairs of lines, where at least the lines on one side of the connection terminal have a fixed distance between one another with certain tolerances. Due to the fact that the spacing of the clamping blocks laterally with respect to one another can be varied within certain limits, the new connection terminal can be applied to lines whose spacing changes with respect to one another due to the accuracy in fabrication or due to different designs. In the simplest case, flexible or elastic bridges are formed between the casing sections, which are configured to have a zig-zag form, meander form, a wave-like form or the like. In a preferred embodiment, two bridges are provided to form a diamond, where the diamond allows an increase or decrease of the lateral spacing.
With a connection terminal being also subject of the present invention, i.e. having a temperature limiter with arbitrary interconnections between two clamping blocks to which it is connected in series, it is preferred that the temperature limiter comprises two terminal legs that are directly electrically connected at their respective free ends to a respective one of both clamping blocks.
It is an advantage of this measure that it is constructively very simple; both connection elements may be dispensed with if the connection terminal is durably equipped with a temperature limiter.
It is a further object that at least one terminal leg comprises at its free end a fish joint strip that contacts the associated clamping block from the outside.
Here, the simple and safe assembly is advantageous, particularly if the fish joint strip is clamped between the clamping block and an inner wall of a channel of the connection terminal wherein the channel receives the clamping block. Here it is merely necessary to attach a temperature limiter after the clamping block has been inserted into the channel, whereby the fish joint strip slides between the clamping block and the channel wall and gets clamped in this position.
On the other hand, it is an object that at least one terminal leg comprises at its free end a connector eyelet that is connected with the associated clamping block by a screw being provided for clamping one of both lines.
This measure results in a very safe electrical connection between the clamping block and the terminal leg, particularly in those cases wherein the connector eyelet has a smaller diameter than the core diameter at the screw bolt so that the screw screws or even cuts into the connector eyelet and ensures in this way a safe electrical connection between the connector eyelet and the screw. The screw is screwed simultaneously into the clamping block where it is used for clamping a line. Independent from the thickness of the line, the electrical connection between the clamping block and the temperature limiter via the screw is guaranteed, the screw being electrically conductive and being connected on the one side with the clamping block and on the other side with the connector eyelet.
It is also an object that both clamping blocks are arranged along a longitudinal axis one after another and the temperature limiter is received in a frontal receptacle extending transversely to the longitudinal axis.
This measure is advantageous in that the temperature limiter can be thermally coupled to a device to be monitored in a very effective manner. If the electrical device to be monitored is, for example, an electrical motor winding, the clamping block can be directly attached with its front end onto the windings, whereby the temperature limiter is electrically isolated from the windings merely by the outer wall of the casing of the connection terminal, but apart from that the temperature limiter is in close thermal connection to the windings. Thus an effective and fast response is provided for.
The invention further relates to an electrical device provided with a new connection terminal, where the connection terminal is fixed to the housing of the electrical device or alternatively, the connection terminal is formed integrally with the housing.
Further, the invention relates to a temperature limiter with an actuator member arranged thereon or an actuator member independent of the temperature limiter for use in the new connection terminal.
Further advantages and features will become apparent from the following description and the attached drawings.
It will be understood that the above-mentioned features and those to be discussed below are not only applicable in the given combinations but may also be used in other combinations or taken alone without departing from the scope of the present invention.